These post are fun to me also. My favorite are the mechanical and great bus adventures. I find it amazing how many new things one can learn everyday, now if I could just remember some of it!!!!What Clifford is saying in different words that there are several gear ratio in the gears at the drive end of the blower. The factory used different one over the years. 1.95 to 1, 2 to 1 , 2.05 to 1 are some numbers I think I remember for blower speeds.

Old get Away - Like Tom C said a 60 numbered injector probably would have been a better choice. Do you know if your cam timing is Std or Adv. If Adv the DD book says 1.484 inj timing, I cleaned up a smoking engine by going to 1.470 injector height setting. If you have Standard timing then I would try per the book a setting of 1.460. Tom C has a friend in Bakersfield, CA named Don Fairchild that is a whiz kid on these I would talk to him. Luke in New Jersey is another excellent source. I am sure others on this board can recommend someone close to you.

I am just making a lot of guess from afar.If your engine only smokes when sitting for days and it is different then just sitting overnight. Plus if the weather is warm enough in both examples for complete combustion at start up. Does your engine start immediately or turn over some before staring as it is injecting fuel that is not burnt--like weak batteries. Another thing if your check value on the main line is leaking, small leak letting air in the system, maybe fuel pump seal or worned shaft. Are you even back at the engine when it starts. Does it fire completely smooth immediately or minor roughness while smoking and then smooths out at the same time it stops smoking. Are you using oil Detroit's always use some oil if not something is wrong such as a cross over fuel line under the value cover could be sucking air sitting and adding diesel to the oil while running, diluting your oil. Pretty soon no run ever again without big money transfusion. Sorry for poor joke. If you have any doubt on this, a oil sample will show diesel fuel percentage in oil and the current weight of the oil. Example of 3.5% fuel dilution will make a Delco 40wt oil come back at less then a 20 wt oil. Not trying to scare you but so many possibilities. My current bus engine it took forever to find my problem. It was 2 things. one the check value and worn shaft from the fuel pump.If it runs rough when starting take the return line off after the restricted fitting on the return line this fitting will be stamped in something like this "R80" put this in a bucket hold line against the side. You are looking for any air bubbles or fuel that almost looks like foam during the start up and if the bubbles clear up about the same time the engine smooths out.If you have a DD Service Manual look in #2 Fuel Section, Section 2.0 troubleshooting it will tell you a lot about what I mentioned above and much more. Cliffordthis info came from a May 1994 book same section as above. pg.8 I was thinking the same thing as you about the N65 brown & white having different min to max. fuel outputs, but they both have same settings of 64 to 69. This page shows that you are correct that not all 65 injectors have the exact same fuel output it list several 65'. Last night I was looking in a inline 671 book of about 1972 vintage and it listed more injectors. Higher output M's, NH65-70 to 72, lower 7E65 63 to 68, it seem 64 to 69 is the most common for N, C, B in the 1994 book and more in other books. 1994 book pg 10 talks about 3 different types of plungers. "The fuel output and the operating characteristics of an injector are to a great extent determined by the type of plunger used" "The lower helix angle retards or advance the end of the injection period" Do not mix these plungers in overhaul of an injector or spray tips. "erratic operation will results and may caue serious damage to the engine or equipment it powers"Page 20 "The injector fuel output is largely dependent upon the combined output of its plunger/bushing and spray tip assemblies.About 2000 I had some new Green N80's I looked at part numbers and as I remember to change it over to N70' it would only take a plunger. DD told me that no injector parts were in their system anymore. I have someplace a double sided chart that list several injectors and the various DD part numbers it was interesting to see what the differences were between the different injectors. Did it tell me the exact answer we are looking for in black and white, I would say no. Page 12 talks about spray tips with specific numbers stamped on them what their flows rates are. examples 6-.006 flow is 22, 7-.007 rate 69, 8-.0055 rate 26, 8-.006 rate, 9-.0055 rate 48, 9-.0058 rate is 69. As I remember the first number is the numbers of holes & second is diameter of each hole. I will look for the the above chart, scan it and e mail the chart to anyone that can post it if anyone is interested.

OneLapper, as I recall, the advanced timing was two teeth, not one tooth. I often wondered why I did not see anyone refer to advancing by one tooth.

Now I have. Are you sure that you want to use this setting?

For what it's worth.

Tom Caffrey

Ugh. I'll get in touch with the tech I talked to and ask about the number of teeth to advance the timing. I thought I read it in the tech manual. I may have gotten it completely wrong which is a distinct possibility. I never counted the actual teeth, but it's difficult to make heads and tails of the pictures.

The engine block is a replacement block according to the serial number stamped on it. It comes up as a 1981. When did they stop making these engines? I plan on removing the back cover to check over the cam timing so I hope to find timing marks on the gears.

Can anyone lead in the right direction to find a chart of hp & torque ratings for an 8V71? I'd like to see how much difference there is between N60 std timing and N65 advance timing.

Another thing: How many of you guys are running without mufflers? I passed a purple 4106 with "straight pipes" on the highway some time ago and it sounded GREAT! Might too loud inside, though. I have a 4" inlet/outlet muffler that doesn't seem to flow enough. It's popped of three times. Each time I felt a surge of power, then heard the noise!

The engine block is a replacement block according to the serial number stamped on it. It comes up as a 1981. When did they stop making these engines? I plan on removing the back cover to check over the cam timing so I hope to find timing marks on the gears.

Can anyone lead in the right direction to find a chart of hp & torque ratings for an 8V71? I'd like to see how much difference there is between N60 std timing and N65 advance timing.

Another thing: How many of you guys are running without mufflers? I passed a purple 4106 with "straight pipes" on the highway some time ago and it sounded GREAT! Might too loud inside, though. I have a 4" inlet/outlet muffler that doesn't seem to flow enough. It's popped of three times. Each time I felt a surge of power, then heard the noise!

Actually they still make them! But not for the general public! Big industry and military are the only ones with access to NEW ones!

4" inlet? hmmm sounds small to me! Shoot my pick up truck has 4" from the Doug Thorley headers back!

And if you run the pipes to where they stick out past the back of the bus you should only hear a pleasant (at least to me it is!) vmmmmm inside! FWIW BK

I have black N70 injectors on mine and do not like them, a gift from the PO. I spend too much time looking in the rear view mirror trying to keep the smoke down. My fuel mileage is also not what I would like. One would think that there could be a way to adjust the stroke or rack travel so it would deliver the equivalent of a smaller injector. Why is that not possible?

Logged

L. Christley - W3EYE Amateur ExtraBlue Ridge Mountains, S.W. VirginiaItís the education gained, and the ability to apply, and share, what we learn.Have fun, be great, that way you have Great Fun!

Barn Owl. I would wonder if you have the correct injector and cam timing. But, from everything that I've learned in the last couple of weeks while trying to find the answers to my injector questions, it seems like N70 injectors would be used on Turbo engines only. Do you still talk with the PO? Might be a question for him.

LarynI think it would be best to change injectors. I am not recommending any of the following. You asked I have seem the following in the book only. May 1977 DD book Section 14.14 , pg 1 Supplementary Governing Device Adjustment---Engine Load Limit Device. Pg 2 Power Control Device.Another thing I noticed is to adjust the high speed this requires a different spring for the lowest settings. See the "The Governor Settings for TT engines. This in the 1994 book inline 671 they reduce the power up to 83%. I am guessing that might help some. Sec. 14.3.5 pg. 1 & 2.Both of these the book is calling the engines to be tested on a Dyno.If you talk to a DD whiz, I know some have experimented with injector height settings. I once had a inline 671 that smoked a little under a constant hard load. The book called for 1.484, I was told to set it to 1.470 and it cleaned it up. This is not close to amount of smoke that a N70 is capable of putting out.Do you know if you have Adv. timing? If you had N65's with std timing they say use 1.460 for inj. height instead of the normal 1.484. I have not seen any thing that talks about this for N70's if you have Std timing.You asked for unusual thoughts for your N70's. About 8 or 9 yrs. ago someone posted about Colonial Diesel in I think in Mass. I dealt with them, excellent price and advise. I looked for teir number about 4 years ago, it has been misplaced. Their price was about 1/3 of my local price high injector shop.I would hope you have ADV timing. I wonder if you can recycle unburned diesel back to the tank!!! Just kidding.

MarkSorry to pick on you again. All of the following info. is for Non Turbo 71 certified automotive engines. Each year various recommendations changed. With Adv. cam timing. This info is from various manuals books between 1967 to 19941978 was the last year for C70 injectors.1972 was the last year for N70 injectors. 1973 and 1972 inj. ht. is 1.484 and 1970 and 1971 inj. ht. is 1.460You will find this try of info. in the Tune up section usually next to the last section in the book. Sec. 14The N70 were not even in the tune up section for the turbo engines. Before smog rules came along.

CraigC, I don't feel picked on so don't worry about that! I'm interested in the N65 injectors, Advancing the cam timing and maybe playing with the injector timing a little bit. I'll let you know how things progress. I still have to compression test things, look at mains and conrod bearings, look at the blower situation (heavy scores in the lobes), etc. Tons to do.

Update: I tried to contact the PO but no response yet. He didnít seem to know much anyways when I first bought the bus because he said too many years had passed. I do know that he had a local marine shop do most of his service and one time had an engine swap done. I can only hope it is advanced timed. I have spoken to an old Trailways mechanic (Ricky Hall) who lives south of me and he said he would be willing to do a tune up. He is in his eighties and still tinkers with detroits on occasion. I told him about my miserable fuel mileage and he said he thought it was about right and that most exaggerate what they get. I am not so sure about that because my Father's bus gets better than mine and he has more hp. I am wondering if I might have some dribbling injectors. I would love to change them but there is just no way I can justify it. I am lucky if the bus goes out three times a year on what are relatively short trips. I just have too many mouths to feed at this stage in my life. One step at a time I suppose. I will continue trying to contact the PO. Thanks for your input.

Laryn

Logged

L. Christley - W3EYE Amateur ExtraBlue Ridge Mountains, S.W. VirginiaItís the education gained, and the ability to apply, and share, what we learn.Have fun, be great, that way you have Great Fun!

Mark you do know that a 2 strokes has to be running at 600 rpm to do a compression test that's the DD way

Uh, I did not know that. I learn something new. Well, I'll have to figure out if I'm rigging up the engine to run while it's on the pallet or cheat and just crank it over to check the delta between the cylinders.

Starting the engine isn't the hard part, it's rigging up some type of radiator. Maybe just a hose forcing water through the engine, or long hoses going to a 55 gallon drum filled with water?